A damping valve is used in a shock absorber for a vehicle, for example. The damping valve includes an annular leaf valve that opens and closes an outlet end of a port formed in a piston of the shock absorber. A plurality of leaf valves are provided, and the leaf valves are disposed so as to be laminated in an axial direction.
The leaf valve is configured such that an inner peripheral side thereof is fixed and an outer peripheral side thereof deflects. The port of the piston is opened and closed by the outer peripheral side of the leaf valve. When a flexural rigidity of the leaf valve provided in the damping valve is set to be low, a damping force generated at a low piston speed is excessively small. When the flexural rigidity of the leaf valve is set to be high, on the other hand, the damping force generated at medium and high piston speeds is excessively large. It is therefore difficult with the damping valve to achieve passenger comfort in the vehicle in all speed regions.
JP2011-64285A discloses a damping valve including: a leaf valve that opens and closes a port of a piston and includes a plurality of cutouts; a guide member disposed adjacent to the leaf valve in order to fix an inner peripheral side of the leaf valve; a main valve disposed on an outer periphery of the guide member to be free to slide; and a plate spring attached to the outer periphery of the guide member in order to bias the leaf valve to the piston side via the main valve.
In a shock absorber including the damping valve described above, when the piston speed is low, the leaf valve does not deflect, but working oil discharged from the port in the piston passes through the cutouts in the leaf valve so that a comparatively large damping force can be secured. When the piston speed reaches a medium or high speed, a pressure of the working oil passing through the port in the piston acts on the leaf valve so that the outer peripheral side of the leaf valve deflects against a biasing force of the plate spring. As a result, the port opens widely so that the damping force is prevented from becoming excessively large. Thus, an improvement in the passenger comfort of the vehicle can be achieved in accordance with the piston speed.